Locomotion: Structural Properties

Transcription

1 Locomotion: Structural Properties

2 Perfusion and O 2 Delivery to Muscle Muscle activity influences oxygen extraction from the blood in many ways: Reduction of local [O 2 ] by aerobic respiration Production of CO 2 and subsequent changes in ph Metabolite (ex. 2,3-DPG) production All result in O 2 release from Hb

3 Capillary Networks Rate of diffusion from RBC to mitochondria depends on : Steepness of the gradient Diffusion distance Diffusion distance determined largely by capillary geometry: Short in aerobic muscles Greater in glycolytic muscles

4 Myoglobin Myoglobin (Mb) = oxygen-binding heme protein found in aerobic muscles. 2 major roles: intramuscular oxygen store oxygen transport Release oxygen when tissue oxygen levels decrease. [Mb] high in animals that regularly experience hypoxic conditions

5 Myoglobin Once oxygen crosses the muscle cell membrane, is rapidly bound to Mb. Reduces [free O 2 ] in cell and helps maintain oxygen gradient. Mb bound O 2 may then act as a store, or facilitate O 2 diffusion to mitochondria.

6 Vertebrate Skeletons Muscles generate force of contraction for movement, but must act on some sort of skeleton Most vertebrates possess endoskeletons Composed of different combinations of bone and cartilage

7 Vertebrate Skeletons Catilagenous skeletons are found in the ancient fish (agnathans & chondrichthians) HAGFISH ½ meter WHALE SHARK: 12.6 meter / 36 tonnes

8 Vertebrate Skeletons More recent fish and tetrapods possess skeletons of bone and cartilage. OARFISH : 17 meters long

9 Vertebrate Skeletons Ligaments and tendons hold the musculoskeletal system together. Ligaments hold one bone to another Tendons attach muscles to bone Important in locomotion: Interconnect different elements of system Ensure correct positioning of muscles Help transmit forces between musculoskeletal elements.

10 Skeletal Components Long bones in locomotor appendages meet and articulate at joints Joints are often bathed in synovial fluid: reduces the degree of friction Determine range of movement. Ball & Socket Joints Hinge Joints

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12 Skeletal Components Muscles work in combination with bones to create levers All mechanical and biological levers have 3 elements: Fulcrum point of rotation joint Weight force exerted by object to be moved Force - force generated muscle contraction

13 Mechanical Power Mechanical power (P) is the product of force (F) generated by a muscle and shortening velocity (V). P = F * V Short thick muscle = Sarcomeres arranged in parallel Produces great deal of force with low velocity. Long thin muscle = Sarcomeres arranged in series Muscle shortens faster with less force.

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15 Elastic Storage Energy When muscles shorten, some of the force that is used to stretch connective tissue and bend limbs at their joints is stored as elastic storage energy Energy is stored in the tendons as animals run, bound, hop, gallop, etc.

16 Elastic Storage Energy 4sE&feature=related

17 Locomotion: Moving in the Environment

18 Gravity & Buoyancy Gravity is the element of the physical environment that has the greatest impact on locomotor strategies Gravity exerts the greatest effects on terrestrial animals (full weight of gravity) Aquatic animals reduce the effect of gravity by buoyant forces.

19 Buoyant Forces Buoyancy = an upward force that counteracts the effects of gravity. the tendency to float. Body density is determined by body composition: Bones & Cartilage = highest density Proteins = slightly more dense than water Lipids = slightly less dense than water Gases = lowest density

20 Lipid Stores Chondrichthians use lipids to increase their bouyancy. Accumulate high levels in their livers: highest in pelagic sharks (neutrally bouyant) lowest in benthic rays (slightly negatively bouyant)

21 Swim Bladders

22 Fluid Mechanics An object moving though water creates a complex pattern of flow. Fluid mechanics = rules that describe the movement of a fluid.

23 Laminar and Turbulent Flow Cost of Locomotion Greatly Increased

24 Reynolds Number Transition from laminar to turbulent flow depends on the properties of the: Fluid: Object: Movement: density & viscosity size & shape velocity & direction Reynolds Number (Re) calculation: Re = VLp/µ

25 Orientation and Turbulent Flow

26 Drag Drag = forces that oppose forward movement. For an animal to move through a fluid, it must overcome drag. Two types of drag are encountered: Friction drag interaction of surface and fluid. Pressure drag force required to redirect the fluid around the object.

27 Streamlining The shape of an object is important to pressure drag. Streamlining reduces the amount of energy animals require to overcome pressure drag. Most larger swimmers and fliers have streamlined body shapes that reduce drag

28 FLAT PLATE SPHERE TEARDROP

29 Streamlining

30 Fitness Ratio

31 Wave Drag

32 Aerodynamics & Hydrodynamics Swimmers and fliers face similar challenges when moving through their environment: Overcome gravity to maintaining position Locomotor strategies must be matched to physical properties of medium (air v. water) Both benefit from streamlining Use appendages to control movement of fluids over their body.

33 Lift Wings and fins control the path of movement of their surrounding medium Most wings and fins possess the shape of an aerofoil or hydrofoil:

34 Lift Shape is critical to producing lift, or an upward force.

35 Lift

36 True Flight vs. Gliding True flight includes flapping, hovering flight and soaring. In true flight, wing movements generate fluid movements that allow the animal to control velocity and altitude. Gliding also involves structures to alter fluid movement, but the animal inevitably descends toward the ground.

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38 Soaring Flight In some large birds (albatross, condor, etc.) wing structure is much better suited for soaring flight than flapping flight.

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40 Fin & Wing Shapes Fin and wing shapes influence fluid movements. Diversity of fin and win shapes reflect the effects of the physical environment and biological properties of each species.

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43 Terrestrial Movement Main challenge to locomotion = gravity Terrestrial animals require strong bones and postural musculature. Amphibians and Reptiles: Typically lie directly on the ground reducing costs of fighting gravity. Birds and Mammals: Use their limb muscle to lift their bodies off the ground, requiring physiological investment.

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45 Energetics of Movements Cost of Transport (COT) Parameter of metabolic demand of exercise How much energy does it cost and animal to move a particular distance?

46 Cost of Transport COT = metabolic rate locomotor velocity = ml of O 2 per min m per min = ml of O 2 per m

47 Cost of Transport COT total does not take into account RMR Net COT is Total MR RMR Used to determine the velocity at which animals move most economically through their environment for a given distance.

48 Velocity and COT

49 Style of Movement and COT Many animals utilize different styles of movement over different velocities. Ex. Pony experiment (Dick Taylor) How animals change gaits to alter interaction between velocities and energetics

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51 Environmental Determinants Cost of locomotion differs greatly for swimmers flyers and runners Costs are lowest for swimmers and highest for runners Reasons for these differences are related to efficiency of movement.

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56 Body Size and COT